Quantum limits to the sensing of magnetic and magnetic-like fields

by Morgan Mitchell (ICFO)

Wednesday 2 Sept 2026, 14:00 → 15:00 Europe/Zurich

4/3-006 - TH Conference Room (CERN)

Fundamental physics has motivated much work in quantum sensing, notably the generation of squeezed light to use in interferometric gravitational wave detectors and deep studies of the problem of phase estimation, often described as the core problem of quantum sensing. Fundamental physics increasingly employs precision measurements to search for physics beyond the Standard Model. This motivates work on precise detection of weak fields, which can signal the existence of as-yet-undetected particles and forces. Detection of the magnetic field is a paradigmatic example of field detection, for which there is abundant practical experience and - for specific sensors - model-based quantum sensitivity limits. These field-sensing limits look very different from phase estimation limits: For example, color-centre ensembles [1] and atomic vapors [2] are known to have sensitivity limited by the volume of the region over which the sample is measured, with no dependence on a quantum information resource like particle number. For dc-SQUIDs, a similar limit concerns the area over which the flux is measured [3]. Until recently, all demonstrated dc field sensors obeyed a geometric limit of this kind.  I will describe what is known and is not known about such limits [4], describe recent work on exotic sensor technologies without such limits [5] and a planned experiment to apply an exotic field sensor to searches for new physics [6].

1. [1]  Morgan W Mitchell. Scale-invariant spin dynamics and the quantum limits of field sensing. New Journal of Physics, 22(5):053041, may 2020.

2. [2]  Ricardo Jiménez-Martínez and Svenja Knappe. Microfabricated Optically-Pumped Magnetometers, pages 523–551. Springer International Publishing, Cham, 2017.

3. [3]  Claudia D. Tesche and John Clarke. dc squid: Noise and optimization. Journal of Low Temperature Physics, 29(3):301–331, 1977.

4. [4]  Morgan W. Mitchell and Silvana Palacios Alvarez. Colloquium: Quantum limits to the energy resolution of magnetic field sensors. Rev. Mod. Phys., 92:021001, Apr 2020.

5. [5]  Silvana Palacios Alvarez, Pau Gomez, Simon Coop, Roberto Zamora-Zamora, Chiara Mazzinghi, and Mor- gan W. Mitchell. Single-domain Bose condensate magnetometer achieves energy resolution per bandwidth below ̄h. Proceedings of the National Academy of Sciences, 119(6):e2115339119, 2022.

6. [6]  Pau Gomez, Ferran Martin, Chiara Mazzinghi, Daniel Benedicto Orenes, Silvana Palacios, and Morgan W. Mitchell. Bose-Einstein condensate comagnetometer. Phys. Rev. Lett., 124:170401, Apr 2020